使此 SQL 查询更好的更简单方法

Question

我在这里有这个 MySQL 查询..

/***
 * An ugly self joining sql.
 * We want the parent's name so we have to join with the same table
 *    joining on child_row.parent_id = parent_row.id
 * Don't remove the LIMIT from this... it might be bad.
 */
$sql = 'SELECT cNode.*, pNode.name as parent_name ';
$sql.= ' FROM t_nodes AS cNode LEFT JOIN t_nodes AS pNode ';
$sql.= ' ON cNode.parent_id = pNode.id ';
$sql.='  WHERE cNode.id = '.$id.' LIMIT 1';

有没有办法让这更优雅？

Answer 1

与 SQL 无关，只是为了提高 PHP 源代码的易读性：

$sql = "
    SELECT cNode.*, pNode.name as parent_name
    FROM t_nodes AS cNode LEFT JOIN t_nodes AS pNode
    ON cNode.parent_id = pNode.id
    WHERE cNode.id = $id LIMIT 1
";

Answer 2

我能想到的唯一合理的选择是一个相关的子查询来获取父名称......

SELECT
  cNode.*,
  (SELECT name FROM t_nodes AS parent WHERE id = t_nodes.parent_id) AS parent_name
FROM
  t_nodes
WHERE
  cNode.id = $id
LIMIT 1